code: def ref_top_k_data_bw(
      x, g, k, abs, reduce, base_axis, largest, with_index, **kw
  ):
      assert not with_index
      return ref_top_k_data(
          x, k, abs, reduce, base_axis, largest, with_index, g
      )[1].flatten()
  
file_path: nnabla/python/test/function/test_top_k_data.py
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import list_context, function_tester
label_desc: Use image node_id 3 for calling a global function with example usage: ref_top_k_data_bw(x, g, k, abs, reduce, base_axis, largest, with_index) and returns: ref_top_k_data